SPIKE/POC - CSR-137 multi step form

@mikejw 

Pull Request for POC so you can easily see changes.

### DO NOT MERGE
Did solve my issue!

From the Friend of Symfony Rest Bundle docs https://github.com/FriendsOfSymfony/FOSRestBundle/blob/master/Resources/doc/6-automatic-route-generation_multiple-restful-controllers.md